gradle build not generating jacoco test report

In my gradle build script, I have a section which says to generate a test report when I run task : jacocoTestReport

jacocoTestReport {
    group = "build"
    reports {
        xml.enabled false
        csv.enabled false
        html.destination "${buildDir}/reports/coverage"
    }
}

When I run the task, it gives me an error : Unable to read execution data file ..\build\jacoco\test.exec How can I fix this error. When I do gradle build on the complete project, I see test report is getting generated.